title: Group I mGluR-regulated translation of the neuronal glutamate transporter, excitatory amino acid carrier 1.
abstract: Recently, we demonstrated that mRNA for the neuronal glutamate transporter, excitatory amino acid carrier 1 (EAAC1), is found in dendrites of hippocampal neurons in culture and in dendrites of hippocampal pyramidal cells after pilocarpine-induced status epilepticus (SE). We also showed that SE increased the levels of EAAC1 mRNA ~15-fold in synaptoneurosomes. In this study, the effects of SE on the distribution EAAC1 protein in hippocampus were examined. In addition, the effects of Group 1 mGluR receptor activation on the levels of EAAC1 protein were examined in synaptoneurosomes prepared from sham control animals and from animals that experience pilocarpine-induced SE. We find that EAAC1 immunoreactivity increases in pyramidal cells of the hippocampus after 3 h of SE. In addition, the group I mGluR agonist, (S)-3,5-dihydroxyphenylglycine (DHPG), caused an increase in EAAC1 protein levels in hippocampal synaptoneurosomes; this effect of DHPG was much larger (~3- to 5-fold) after 3 h of SE. The DHPG-induced increases in EAAC1 protein were blocked by two different inhibitors of translation but not by inhibitors of transcription. mGluR1 or mGluR5 antagonists completely blocked the DHPG-induced increases in EAAC1 protein. DHPG also increased the levels of glutamate receptor 2/3 protein, but this effect was not altered by SE. The DHPG-induced increase in EAAC1 protein was blocked by an inhibitor of the mammalian target of rapamycin or an inhibitor of extracellular signal-regulated kinase. These studies provide the first evidence EAAC1 translation can be regulated, and they show that regulated translation of EAAC1 is up-regulated after SE.
authors.affiliation: Departments of Pediatrics and Pharmacology, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Ross
authors.forename: Hariharasubramanian
authors.initials: H
authors.lastname: Ramakrishnan
authors.forename: Brenda E
authors.initials: BE
authors.lastname: Porter
authors.forename: Michael B
authors.initials: MB
authors.lastname: Robinson
mesh_terms: D000818:Animals; D015153:Blotting, Western; D003292:Convulsants; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D050580:Excitatory Amino Acid Transporter 3 / Q000096:biosynthesis* / Q000235:genetics*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors; D005455:Fluorescent Antibody Technique; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism*; D010862:Pilocarpine; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D013226:Status Epilepticus / Q000139:chemically induced / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors
chemical_list: D003292:Convulsants; D050580:Excitatory Amino Acid Transporter 3; C578937:Grm5 protein, rat; D011725:Pyridines; D012333:RNA, Messenger; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; C493398:Slc1a1 protein, rat; C104077:metabotropic glutamate receptor type 1; D010862:Pilocarpine; D008734:Methoxyhydroxyphenylglycol; C121465:6-methyl-2-(phenylethynyl)pyridine; C546845:mTOR protein, rat; D058570:TOR Serine-Threonine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; C010117:3,4-dihydroxyphenylglycol